Depends on which side of the river I work on, Iowa or Nebraska. Disclaimer: my varsity has been all Iowa so far, so I can't speak for the Nebraska, whilst my subvarsity has been all Nebraska. (Don't ask about this odd quirk!)

Varsity: $40-50/game (I usually end up working boy/girl doubleheaders)
Subvarsity: $40/game (Metro Association-I end up negotiating this from the smaller schools as well)
JH: $30/game, and (if I recall right) $45 for a doubleheader (sometimes the B game is a running clock or shorter periods)
No mileage at the varsity level, though I hear some schools MAY be willing to do it if negotiated.